MQCT: User-ready program for calculations of inelastic scattering of two molecules

Abstract

A program named MQCT is developed for calculations of rotationally and vibrationally inelastic scattering of molecules using the mixed quantum/classical theory approach. Calculations of collisions between two general asymmetric top rotors are now possible, which is a feature unavailable in other existing codes. Vibrational states of diatomic molecules can also be included in the basis set expansion, to carry out calculations of ro-vibrational excitation and quenching. Minimal input for the code assumes several defaults and is very simple, easy to set-up and run by non-experts. Multiple options, available for expert calculations, are listed in the Supplemental Information. The code is parallel and takes advantage of intrinsic massive parallelism of the mixed quantum/classical approach. A Monte-Carlo sampling procedure, implemented as option in the code, enables calculations for complicated systems with many internal states and large number of partial scattering waves. The coupled-states approximation is also implemented as an option. Integral and differential cross sections can be computed for the elastic channel. Rotational symmetry of each molecule, as well as permutation symmetry of two collision partners, are implemented. Potential energy surfaces for H2O + He, H2O + H2, and H2O + H2O are included in the code. Example input files are also provided for these systems. Program summaryProgram title: MQCTProgram files doi:http://dx.doi.org/10.17632/sg36r35njz.1Licensing provisions: GNU GPL v3.0Programming language: FORTRANSupplementary material: MQCT user guideNature of problem: Calculations of rotationally and vibrationally inelastic scattering of two molecules, with possible applications in astrophysics and atmospheric chemistry.Solution method: Mixed quantum/classical theory (MQCT) approachAdditional comments: This code can be used to simulate a collision of two asymmetric top rotors, such as H2O + H2O.